Ben and I have an action item to make a proposal for Guideline 1.3 Level
1 Success Criterion 2 [1]:
"When information is conveyed by color, the color can be
programmatically determined or the information is also conveyed through
another means that does not depend on the user's ability to
differentiate colors."
Some people raised questions of how this SC is different from the level
2 SC in practice. While it is possible to imagine that color could be
programatically determined and the existence of color presented by a
non-visual user agent, we've been unable to come up with sufficient
techniques that would reliably convey color information to users of
assitive technology today.
Without additional structure or role information like the role attribtue
in XHTML 2.0, it is somewhat difficult to imagine that AT will include
mechanisms for identifying and utilizing color attributes in a
meaningful way (e.g., informing of every color change or providing
mechanisms for flagging a specific color and announcing it whenever it
occurs in subsequent content). We also felt that the overlap of this SC
with it's level 2 couterpart [2] is likely to cause confusion.
Currently, there are two techniques listed as sufficient for the level 1
SC that are not also listed in the level 2 SC:
1.) Using text and text formatting (e.g. unicode text with color
styling) AND using the same colored text in the legend or instructions
introducing the use of color.
2.) Using features of the technology to ensure that color attributes
are available via the accessibility API.
Today, we're not sure that the use of either of these techniques meet
our definition of programmatically determined since we couldn't come up
with any examples of assistive technologies that would allow the color
information to be recognized reliably.
It really seems like the best thing to do is to remove this Level 1 SC,
and promote the Level 2 SC to Level 1. In other words, the Level 1 SC
for color in Guideline 3.1 would be:
"Any information that is conveyed by color is visually evident when
color is not available."
The objections raised about this proposal have been that this SC impacts
design freedom by imposing requirements on color and violates our rules
for level 1. However, even the existing SC places constraints on color
in that it would require authors to write instructions like:
"Please fill out the form below. Required fields are marked in <span
class="red">red</span>."
rather than:
"Please fill out all of the <span class="red">required fields</span> in
the form below."
The guide doc would be the existing one available at [2] with the
addition of the following sufficient technique:
Using structure where color color encoded information is used.
The wording could use some work, but the idea would be to say that it is
sufficient for authors to pass using things like <strong
class="red">required</strong> or <em class="red">required</em>, but that
the examples above (using <span>) would not be sufficient. It would also
explain that authors could style the <em> or <strong> to remove the
default italic or bold styles if they prefer, making the use of this
technique invisible (thus meeting our rules for level 1).
[1] http://trace.wisc.edu/wcag_wiki/index.php?title=Guide_to_1.3_L1_SC_2
[2] http://trace.wisc.edu/wcag_wiki/index.php?title=Guide_to_1.3_L2_SC_2
- Michael and Ben
--- Signature ---
Michael Cooper
Accessibility Product Manager, Watchfire
1 Hines Rd Suite 200, Kanata, ON K2K 3C7 Canada
Tel: +1 (613) 599-3888 x4019
Fax: +1 (613) 599-4661
Email: michaelc@watchfire.com
Web: http://www.watchfire.com/